The invention relates to a process for burning fuel comprised of free hydrocarbons and/or fine-grained to dusty solid fuels, in particular in a metallurgical vessel. Furthermore, the invention relates to a burner for carrying out the process and a metallurgical vessel including a burner according to the invention.
Various types of construction are known of burners for burning gaseous, liquid or fine-particle solid fuels, in which oxygen or an oxygen-containing gas is supplied to the burner mouth separate from the fuels. Thus, for instance, from WO 91/06804 an oil burner is known, in which liquid fossile fuels emerge through a central tube and oxygen emerges through discharge openings provided radially about the central tube and parallel thereto, wherein a partial amount of the oxygen is allowed to emerge from the burner at a low speed and the remaining oxygen is allowed to emerge from the burner at a high speed. This is to avoid nitrogen oxides.
From EP-A-0 347 002 a burner is known, in which oxygen, by means of several oxygen jets which are directed against the axis of the burner at an angle of between 20.degree. and 60.degree., is supplied towards solid fuel blown in centrally in the axial direction of the burner. This causes turbulences and the intimate mixing of the oxygen with the fine-particle solid fuel. This involves the disadvantage that, due to the substantial higher combustion speed of combustible gases externally surrounding the burner or burner jet as compared to the combustion speed of the fine-particle to dusty fuel, poor burning out of the fine-particle to dusty fuel supplied takes place. That known burner, furthermore, has the disadvantage of causing whirling with the oxygen immediately upon emergence of the fine-particle fuels from the central inner tube such that a focal spot is formed located closely at the burner mouth. This causes a high thermal load on the burner mouth and hence extensive wear.
A burner with which such an extensive wear is avoided is known from EP-B-0 481 955. In the burner known from that document, the supply of fuel is effected centrally and oxygen feeding occurs by means of oxygen jets peripherally surrounding the central fuel jet and inclined relative to the central fuel jet, the point of intersection of the oxygen jets with the fuel jet being located at a distance from the burner mouth.
A multi-media nozzle which may be employed also as a burner is known from DE-C-42 38 020. That known multi-media nozzle serves to introduce gaseous, liquid or pneumatically conveyable solid fuels as well as oxygen, the supply of the substances being effected through a central tube and through one or several annular gaps surrounding the central tube and defined by tubes arranged concentrically with the central tube. However, this involves problems with regard to the thorough mixing with the oxygen of the fuels supplied to the multi-media nozzle.
From DE-A-36 12 682, JP-A-61-062704 and EP-A-0 368 829 it is known per se for axes of fuel jets from burners to be directed such that they are oriented in a skew manner relative to the axes of other jets emerging from the burner, for example in a skew manner relative to a central main jet of the burner. Yet, in this, the arrangement is always chosen such that the fuel jets which are oriented in a skew manner relative to the main jet move away from the main jet from their site of origin onwards.